As a polymer for a cured product that is excellent in properties, such as electrical insulation properties, thermal shock resistance, and adhesion properties, a copolymer (A) having 10 to 99 mole % of a structural unit (A1) represented by the following formula (1) and 90 to 1 mole % of a structural unit (A2) represented by the following formula (2) (provided that the total of all constituent units constituting the copolymer (A) is 100 mole %) is known (see Patent Document 1).
(wherein R11 and R33 each independently represent an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or an aryl group, R22 and R44 each independently represent a hydrogen atom or a methyl group, m1 represents an integer of 1 to 3, n1 and k1 each independently represent an integer of 0 to 3, and m1+n1≦5.)
More specifically, a copolymer (Mw=10,000, Mw/Mn=3.5) consisting of p-hydroxystyrene/styrene/methyl methacrylate=80/10/10 (molar ratio) is described.